A Jones Fracture is clinically described as a fracture approximately 12 mm from the base of the 5th metatarsal. The fracture typically extends laterally across the 5th metatarsal originating at the cuboid/4th metatarsal joint. Background about the history, anatomy and repair of Jones fractures is provided in Fractures of the Base of the Fifth Metatarsal, Foot and Ankle Trauma, 32:171-180, 2001 (Nunley, James A, M.D.), which is incorporated herein by reference.
Jones fractures are often a sports related injury. They commonly occur when an athlete twists the ankle, rolling it laterally over the talus. The resulting forces break the 5th metatarsal.
Jones fractures have a high non-union rate, reported in some studies as up to 50%. There are several reasons for the high non-union rate. A Jones fracture is located in an area of poor blood supply. In addition, several tendons attach in the area, and the tendons tend to pull the fracture apart, causing motion at the site of healing. Complications of surgery are not uncommon, and include damage to the sural nerve and peroneous brevis tendon.
Jones fractures in non-athletes are often treated with a cast or walking boot. The cast or walking boot will typically be maintained for 6-8 weeks, but patients sometimes spend up to 20 weeks in a cast. Often the fracture becomes a chronic non-union and surgery is recommended. Surgery is often performed on athletes in hopes of a quicker recovery and because the nonunion rate is so high. Surgical treatment commonly consists of fixing the fracture with a screw in the center of the intramedullary canal. The surgical technique is challenging mainly because of the shape of the 5th metatarsal bone. The 5th metatarsal has a lateral bow on the dorsoplanter plane and a dorsal bow on the medolateral plane. Additionally, the bone is irregular and pyramid shaped in the vertical cross section. Screw sizing is very important. If the screw is too long, it pierces the medial cortex and can even stress fracture later. If the screw diameter is too small, it will not grab the cortical bone, resulting in poor compression and fixation.
Treatment of Jones Fractures has been a difficult challenge for foot and ankle specialists. Existing systems suffer from various drawbacks, including: screw systems that are not designed specifically for Jones fractures; screws lacking optimal dimensions for Jones fractures; lack of appropriate screw size range; lack of custom instruments; use of cannulated screws, which are not as strong in fatigue as an equivalent solid screw; and use of fully threaded screws, which do not tolerate bending stress as well as a partially threaded screw. The optimal screw type for Jones screws has yet to be defined. See Intramedullary Screw Fixation of Jones Fractures, 22 Foot & Ankle Intl, No. 7, pp. 585-589 (2001). There is thus a need for the surgical kits, instruments, implants and methods having the following characteristics and improvements over the prior art.